client.c

实现udp包传输的client和server

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>

#define PORT 3478

int main(int argc, char *argv[])
{
	if(argc != 2)
	{
		fprintf(stderr,"usage:%s IPaddress\n",argv[0]);
		exit(1);
	}
	
	int sockfd,len;
	int addr_len;
	struct sockaddr_in addr;
	char buffer[256];

	if((sockfd = socket(AF_INET,SOCK_DGRAM,0)) == -1)
	{
		fprintf(stderr,"socket error:%s\n",strerror(errno));
		exit(1);
	}
	
	addr_len = sizeof(addr);
	bzero(&addr,addr_len);
	addr.sin_family = AF_INET;
	addr.sin_port = htons(PORT);
	addr.sin_addr.s_addr = inet_addr(argv[1]); //why?

	while(1)
	{
		bzero(buffer,sizeof(buffer));
		len = read(STDIN_FILENO,buffer,sizeof(buffer));
		sendto(sockfd,buffer,len,0,
			(struct sockaddr *)&addr,addr_len);
		
		len = recvfrom(sockfd,buffer,sizeof(buffer),0,
				(struct sockaddr *)&addr,&addr_len);
		if(len == -1)
		{
			fprintf(stderr,"receive error:%s\n",strerror(errno));
		}
		fprintf(stdout,"receive :%s\n",buffer);
	}	
	
	return 0;
}